Rahman Mujib M, Miyamoto Hiroshi, Takatera Hiroshi, Yeh Shuyuan, Altuwaijri Saleh, Chang Chawnshang
George Whipple Laboratory for Cancer Research, Department of Biochemistry, University of Rochester Medical Center, New York 14642, USA.
J Biol Chem. 2003 May 30;278(22):19619-26. doi: 10.1074/jbc.M210941200. Epub 2003 Mar 20.
Although the progression of prostate cancer initially is dependent on androgens, tumor progression to an androgen-independent growth eventually occurs in most of patients treated with androgen ablation and/or antiandrogen therapy. After the initial response, antiandrogens lose their efficacy and eventually act as agonists to promote androgen receptor (AR)-mediated growth of prostate cancer cells. An aberrant regulation of AR activity, presumably by AR coregulators, may contribute to this acquired agonist activity of antiandrogens. Using an in vitro mutagenesis and a double-negative selection in yeast two-hybrid screening, we have identified a dominant-negative AR coregulator ARA70 (dARA70N), which can inhibit AR transcriptional activity by inactivating the normal function of ARA70 in the LNCaP cells. Whereas ARA70 in oligomeric form interacts with AR and enhances its transcriptional activity, dARA70N lacks AR interaction and might retain the ability to form a non-functional heteromer with ARA70 and interrupt AR transcriptional activity without a change in AR protein itself. The addition of dARA70N reduces the agonist activity and rescues the normal function of antiandrogens in prostate cancer cells. RNA-interference-mediated silencing of ARA70 gene further confirms these observations. Taken together, these findings indicate that ARA70 may contribute to the acquired agonist activity of antiandrogens and plays an important role in making prostate cancer cells resistant to androgen ablation and/or antiandrogen therapy. ARA70 may, thus, be a critical target for developing therapeutic agents against AR-mediated progression of prostate cancer.
尽管前列腺癌的进展最初依赖雄激素，但在大多数接受雄激素剥夺和/或抗雄激素治疗的患者中，肿瘤最终会发展为雄激素非依赖性生长。在初始反应后，抗雄激素会失去其疗效，最终起到激动剂的作用，促进雄激素受体（AR）介导的前列腺癌细胞生长。AR活性的异常调节，可能是由AR共调节因子引起的，可能导致抗雄激素的这种获得性激动剂活性。通过体外诱变和酵母双杂交筛选中的双阴性选择，我们鉴定出一种显性负性AR共调节因子ARA70（dARA70N），它可以通过使ARA70在LNCaP细胞中的正常功能失活来抑制AR转录活性。寡聚形式的ARA70与AR相互作用并增强其转录活性，而dARA70N缺乏与AR的相互作用，可能保留与ARA70形成无功能异源二聚体的能力，并在不改变AR蛋白本身的情况下中断AR转录活性。添加dARA70N可降低激动剂活性，并恢复抗雄激素在前列腺癌细胞中的正常功能。RNA干扰介导的ARA70基因沉默进一步证实了这些观察结果。综上所述，这些发现表明ARA70可能导致抗雄激素的获得性激动剂活性，并在使前列腺癌细胞对雄激素剥夺和/或抗雄激素治疗产生抗性方面发挥重要作用。因此，ARA70可能是开发针对AR介导的前列腺癌进展的治疗药物的关键靶点。
